Fever

Fever: Excerpt from In a Page: Signs and Symptoms

Fever is defined as an elevation of normal body temperature (37°C, or 98.6°F). True fever occurs when the body adopts a new thermoregulatory “set point” secondary to the release of pyrogenic cytokines in response to bacteria, viruses, or other exogenous sources (e.g., malignancy). Hyperthermia, on the other hand, is an elevation of body temperature without resetting of the thermoregulatory mechanism. This occurs when heat production outstrips the body's ability to disperse excess heat.

Differential Diagnosis

• Infection is the most common cause
  –Viral (e.g., influenza, HIV, hepatitis, herpes simplex encephalitis, mononucleosis, adenovirus)
  –Bacterial (e.g., pneumonia, endocarditis, tuberculosis, meningitis, pyelonephritis, appendicitis, cholecystitis, cellulitis)
  –Lyme disease
  –Malaria
  –Syphilis
  –Tularemia
  –Intra-abdominal abscess

• Malignancy
  –Lymphoma (Hodgkin's and non-Hodgkin's)
  –Lymphoproliferative disorders
  –Renal cell carcinoma
  –Leukemia
  –Hepatocellular carcinoma
• Rheumatologic disorders
  –Temporal arteritis/giant cell arteritis
  –Adult-onset Still's disease
  –Systemic lupus erythematosus
  –Sarcoidosis
  –Rheumatoid arthritis
• Drug fever
  –Often temporally associated with the initiation of a new medicine
  –Often associated with a rash (biopsy reveals leukocytoclastic vasculitis)
  –Eosinophilia is common

• Pulmonary embolism
  –Mild fever is often present
  –Other findings of thromboembolic disease (e.g., leg swelling, dyspnea) may be present

Workup and Diagnosis

• Complete history and physical examination
  –In most cases, the cause of fever will be suggested during the history and physical
  –Note characteristics of the fever, maximum temperature, presence of diurnal variation, and recent travel
• Initial laboratory studies may include CBC with differential, electrolytes, BUN/creatinine, glucose, calcium, urinalysis, urine cultures, liver function tests, and ESR
• Blood cultures, including thick smear of the blood to evaluate for parasites (e.g., malaria)
• Chest X-ray may reveal focus of infection (e.g., pneumonia, tuberculosis, malignancy)
• Lumbar puncture for CSF analysis may be indicated
• CT scan of chest and abdomen may reveal an occult infection, abscess, or malignancy
• Echocardiogram is indicated if suspect infective endocarditis or aortitis (syphilis)
• Tagged white cell scans may be used to localize abscess
• Bone marrow biopsy may be indicated if leukemia or a myelodysplastic syndrome is suspected

Treatment

• Initial treatment of fever includes antipyretics (e.g., acetaminophen, NSAIDs)
• Infection should be treated with appropriate antimicrobial therapy and tailored as antibiotic sensitivities are identified
  –Many cases of deep-seated infection or abscess require percutaneous or surgical drainage
• Fever due to malignancy will usually regress with surgical debulking, chemotherapy, and/or radiation directed at the primary tumor
• Rheumatologic disorders may require NSAIDs, steroids, methotrexate, hydroxychloroquine, or other cytotoxic agents
• Dantrolene for malignant hypothermia

Book Source Details

• Book Title: In a Page: Signs and Symptoms
• Author(s): Scott Kahan, Ellen G. Smith
• Year of Publication: 2004
• Copyright Details: In a Page: Signs and Symptoms, Copyright © 2004 Lippincott Williams & Wilkins.

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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.

More About This Book: Title: In a Page: Signs and Symptoms Authors: Scott Kahan, Ellen G. Smith Publisher: Lippincott Williams & Wilkins Copyright: 2004 ISBN: 1-4051-0368-X

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